GS_MASI

Why large aircrafts generally use Hydraulic Powered Actuation Systems?. High hydro-mechanical stiffness and associated high frequency response is relevant for flight control actuation. Additional typical factors are response time and efficiency but not reliability and robustness, when compared with another Systems. High Hydro-mechanical stiffness and associated high frequency response is relevant for flight control actuation. Additional typical factors are good response time, efficiency, reliability and robustness of hydro-mechanical systems when compared with another systems.

Generally, with regards to the number of hydraulic systems used in a civil type certified large aircraft under Part 25 – EASA Airworthiness Regulations: There is no any aircraft using two hydraulic systems. If any primary flight control is require to be hydraulically powered, definitively three hydraulic systems are required. One hydraulic systm if it does not supply any primary flight control. Two independent hydraulic systems if they only supply a single flight control with the rest of the primary flight controls being non powered, or when the flight controls are hydraulically powered but they can be operated by other means (mechanical, EHAS, EMAs) if there is complete lost of hydraulic power. More than 2 independent hydraulic system when all the primary and secondary flight controls are hydraulically operated and there is no manual reversion. Large aircrafts with two engines and three hydraulic systems normally requires a PTU (Power Transfers Unit) to transfer hydraulic power between the hydraulic systems in determined failure cases or for ground taxing with one engine shut down.

Select the correct response(s): Water hammer is negligible in hydraulic system pipe installation. Hydraulic Pumps generally used in aircraft hydraulic systems are gear type and capable to provide roughly same pressure at any flow demand (if below specified max flow demand). Relief valves are used to relieve excessive pressure in a blocked line condition. Relief valves do not react rapidly enough to prevent water hammer excessive pressure spikes. Use of check valves in return lines generally avoids effects of back pressure.

If the aircraft hydraulic system supply the services that control the direction of the aircraft on the ground (e.g. nosewheel steering and differential braking): The emergency braking system must have differential control. The nose wheel steering and normal brakes are supplied by different hydraulic systems.

Common use Aerospace Hydraulic Pumps: Either Engine Driven or Electrical Motor Driven, are normally located in Engine Nacelle. Engine Driven Pump EDP (Variable displacement Pump) usually used as the main power source for hydraulic systems. When engine driven, are installed in engine gearbox. Its suction line and fire shut-off valve in suction line are fire proof tested. Electric Motor Driven pump can be used for normal, backup, emergency and ground servicing operation of hydraulic systems (DC alowws use on ground). Manually operated pumps: backup pump (only for small aircraft), for ground maintenance, to recharge a parking brake acumulator to refill hydraulic systems.

Common use Hydraulic Reservoirs : Do not need pressurization. Vented type reservoir is sufficient whenever located above the pump. Shall be protected by a relief valve. Hydraulic presurrized reservoir utilize system pressure acting on a different piston to achieve the required tank pressure. The hydraulic reservoir is a container for holding the fluid required to supply the system, includinga reserve to cover any losses from minor leakage and evaporation. No hydraulic reservoir shall be located in fire zone. Interior pressure must be enough to avoid pump cavitation. Generally are bootstrap and air pressurized.

The RAT (Ram Air Turbine) is a device that, when deployed, acting as ram air generator. In case of Total Engine Flame Out (TEFO), can provide hydraulic and or electrical power to the essential systems to ensure the aircraft control during its descent until landing. Does not requires a minimum airspeed. Provide power extracting it from the ram air.

Select the correct response(s): The "Priority valve" is a device typically used to isolate the power supply to general services (utility subsystem) when is required to preserve the supply to critical services (generally, primary flight controls). Estoy aquí solo para rellenar.

CFG main advantages compared with VFG are: Less weight. Less frequency changes. Generator efficiency and capability the same in all the frequency range. Not required to hace AC input. Consumers input stage optimized.

The emergency system shall power the services necessary to complete a flight and make a safe landing. The services to be powered must include: Those required for inmmediate safety and which must continue to operate following the loss of the normal electrical power generation systems, without the need for flight crew action. Those required for continued controlled flight. Those required for descent, approach and landing. Those required for take off, climbing and cruise.